Multitube falling film reactors represent today a well established technology, and is frequently the preferred reactorprinciple for sulphonation and sulphation reactions, both giving advanced products; surfactants for the cosmetic and detergent industry. The reactors are assembled according to conventional principles for a multitube shell and tube heat-exchanger with different baffle-arrangements and cooling liquids, with water as the dominating cooling liquid. Typical for all reactors are separate chambers for diluted gas, organic compound, cooling liquid and collection of finished products, chambers mentioned from top of reactor to bottom outlet.
When producing surfactants for the said industry, the gaseous and diluted reactant is sulfur trioxide, typical organic compounds are liquids at 15.degree. C. or higher, the main variety of raw-material being alkylates, fatty alcohols, etoxilated fatty alcohols, alpha-olefins and methyl-esters. Any chemical compound equipped with a socalled flexible hydrogen atom might be sulphonated or sulphated. (Sulphated for all compounds where hydrogen is linked to an oxygen atom, sulphonated for the linkage hydrogen-carbon.)
The overall chemical reactions taking place, are characterized by the fact that diluted, gaseous SO.sub.3 is a very aggressive/reactive reactant, and that the reactions are all extremely rapid and exothermic. Altogether, these properties challenge the control of the molar ratio between the reactants, and only with the very best control of both total and local molar ratio, the best products are achieved. Any deviation in the molar ratio will unavoidably result in increased quantity of undesired by-products, and the main product will suffer from bad colour, lower active matter content, higher content of sulphates, higher content of nonsulphated/-sulphonated organic compounds and consequently lower yield with a higher raw-material consumption. In a MTR, where the numbers of individual and parallel reactor-element could be from two to more than hundred, the most important parameter is the local molar ratio between the reactants, and therefore the best possible and most homogeneous distribution of organic compound to each individual reactor-element. Even the smallest deviation in local molar ratio, can not be fully compensated for later in the process.
To avoid any misunderstanding, total molar ratio is defined as the ratio between the total number of moles SO.sub.3 fed to the reactor divided by the total number of moles organic compound fed to the same reactor. By advanced dosing system for liquid sulfur/liquid sulfur dioxide/liquid sulfur trioxide and finally organic compounds, the total molar ratio can be kept almost constant and without any significant impact on the final product properties.
The local molar ratio, defined the same way but between local flows of said reactants for each individual nozzle-element, is predominantly depending on an even and homogeneous feed, kg/hour of organic reactant to each individual nozzle-set from one common, organic chamber, since a gas carrying a far lower viscosity has a higher tendency of even distribution according to the principle of "the way of lowest resistance". The nozzle-set construction will therefore appear as the decisive and critical element for individual organic flow and local molar ratio. In a MTR, all the nozzle-sets are fed from one common, organic chamber. The nozzle-construction also allows a reactor to consist of only one reactor element, where the total molar ratio becomes equal and identical to the local molar ratio, accuracy only depending on the external dosing system.
Of great and vital importance is also an even and homogeneous distribution of the organic film formed circumferentially on the internal, surface of the female part. This can be achieved, provided that the film distribution/formation on the internal surface of the said female part is determined by the same accuracy as the dosing/metering of organic compounds of the nozzle-set for all reactor elements. It means altogether that the film-formation should be determined by the same accuracy as the dosing/metering of organic compounds, i.e. a well defined annular slot in respect of length an width for all known, operational conditions.
There are several, different concepts of constructions available on the market and already patented, relevant in this connection are following patents:
U.S. Pat. No. 3,918,917 Nitto Chemical Industry Co., Ltd. PA1 U.S. Pat. No. 4,183,897 Construzioni Meccaniche G. Mazzoni S.p.A PA1 FR 2,449,665 Ballestra Chimica S.p.A PA1 EP 0,570,844 A1 Meccaniche Moderne S.r.l PA1 precalibrated and selected/grouped orifices (materials totally different from this patent), characterized by a relatively long distance between the zone for metering/dosing and the zone for film formation. (Pre-selected/grouped orifices should not be mixed up with the terminology nozzle-set and nozzle-set construction described in this document.) PA1 conical or cylindrical slots where even a lower accuracy (compared to this invention) of organic feed only can be achieved through a mechanical adjustment of the slots length or opening by shims. If the slot opening and slot length were well defined in these constructions, and besides appeared with the accuracy described in mentioned patents, no adjustment by shims would be necessary. It is obvious that the location of the male part relatively to the female part by shims, will be influenced by different pressure working on the main flanges/cylindrical plates(pressures different from the conditions during calibration), by the torque on single bolts for tightening, by sealing material and finally by the distance between the cylindrical plates. The fact that all individual nozzle-sets have to be calibrated before start-up, also clearly demonstrates the unsufficient definition of the opening and length of the slots, resulting in a less homogeneous distribution of the film (different thickness around the wetted periphery) on the internal surface of the female part of the nozzle-set. PA1 higher tendency of air-pockets and thereby partly blocking of organic feed during start-up. (Air-pockets in the space between male and female part of the nozzle-set.) PA1 partly more complex components, less easy to machine. PA1 need for time-consuming calibration both before start-up and after an uncontrolled stop during operation, or after a routine washing/cleaning procedure. The accuracy of this calibration will also be influenced by the fact that normal plant conditions are always different from calibration conditions. PA1 generally lower accuracy for individual organic feed compared to the total average of organic feed for all nozzle-sets in operation. PA1 generally will lower accuracy of metering mean increased variation in film thickness. PA1 tightening arrangement for the male and female part of the nozzle-set will influence the accuracy of individual nozzle-set supply and also said accuracy for neighbouring nozzle-sets. PA1 the neccessity of shims adjustment creates very frequently tendency of increased leakages. PA1 accuracy of metering will strongly depend on the torque applied for tightening the bolts. PA1 the individual supply from each nozzle-set will further also be depending on pressure variations during normal operation, pressures working on the different cylindrical plates and giving different impact depending on the location of the nozzle-set on the said plates.
These patents and constructional concepts can be described and grouped by following:
The main differences/disadvantages for already known and operative constructions compared to the nozzle-set construction described in this document, can be summarized by following: